TESTING EVOLUTIONARY THEORIES OF SUICIDAL IDEATION: BARGAINING, COSTLY APOLOGY, AND INCLUSIVE FITNESS

With suicide as a growing concern in model society, evolutionary psychology seeks to understand this concept through the inclusive-fitness model (IFM), the bargaining model (BRM), and the costly apology model (CAM). Although much research has provided evidence for the first two models, few studies have studied the newly proposed CAM or investigated age as a moderator for these models. Furthermore, studies have yet to target two facets of the BRM, physical proximity, and unmet needs. The current studies filled this gap in research with both studies briefly assessing all three evolutionary models through assessing suicidal ideation with burdensomeness, severe transgressions, and social support. Study 1 investigated the relationship between physical proximity and suicidal ideation and the effect age has on the model predictors whereas study 2 examined the relationship between unmet relationships and suicidal ideation in young adults. Results provided evidence for all three models with suicidal ideation correlating with burdensomeness (r = .63, p < .01), severe transgressions (r = .22, p < .01), and social support (r = -.28, p < .01). Furthermore, study 1 revealed that although physical proximity may not be a significant predictor of suicidal thoughts, age likely moderates the strength of the predictors of these models. Lastly, study 2 results supported the BRM through the correlation between unmet expectations and suicidal ideation (r = .45, p < .01). These results indicate that these evolutionary models predict suicidal behavior in young adults, suggests burdensomeness, severe transgressions, unmet expectations, and lack of social support predicts suicidal thoughts, and deepens the literature of suicidal behavior to aid intervention and prevention efforts.